In recent years, studies have been intensively carried out for such a light emitting device that generates incoherent illumination light by using an excitation light source for generating excitation light to irradiate a light emitting section including a fluorescent material, to thereby generate the incoherent illumination light. As the excitation light source, a semiconductor light emitting element is used, such as a light emitting diode (LED), a laser diode (LD), or the like.
As an example of techniques for such light emitting device, the patent literature 1 is disclosed.
The light source device of Patent Literature 1 includes a laser diode for emitting a laser beam of a short wavelength, a collimator for collimating this laser beam from the laser diode into a parallel luminous flux, a condenser for converging the laser beam of the parallel luminous flux from the collimator, and a fluorescent material absorbing the laser beam converged by the condenser and emitting incoherent light as natural emission light. Therefore, in the light source device of Patent Literature 1, the fluorescent material absorbs the laser beam which has large amount of light but serves as coherent light, and naturally emits the incoherent light.